The invention relates to a remote control receiver for the reception of command signals of different operating frequencies, each in an individual channel. The receiver has a plurality of outputs, each assigned to one of the channels, a control signal being produced at a particular output upon the reception of a command signal having the corresponding operating frequency.
In a remote control receiver of this kind, the command generated by the associated transmitter and intended to produce a signal at a particular output of the receiver is expressed by the frequency of the transmitted signal. Therefore, the receiver must be able to recognize this operating frequency accurately to produce the desired control signal from the output associated with this frequency. Resonant circuits tuned to one of the operating frequencies emitted by the transmitter may be used to identify the various frequencies.
However, the setting up of a remote control receiver equipped with resonant circuits requires much labor to tune the various resonant circuits. The detuning of the resonant circuits, which is inevitable in the course of time, makes it necessary to repeat the tuning process after the receiver has been in operation for a certain period of time. Another disadvantage of receivers equipped with resonance circuits is that the coils needed in the resonant circuits require signification space. The disadvantage of this factor increases with the number of operating frequencies to be identified. But the use of coils is also disadvantageous since such a remote control receiver cannot be produced by integrated circuit technology because, from a practical viewpoint, the coils cannot be made by this technology.
Resonant circuits have the further disadvantage that, in principle, they respond to any oscillation whose frequency equals the resonance frequency. Therefore, if a spurious signal is in the operative frequency range of the receiver, for example, a control signal will be generated at the respective output in response to this spurious signal. In other words, spurious and noise signals may also trigger generation of a control signal in an undesired manner. Another disadvantage of resonance filter selection is that the receiver sensitivity is maximum only at the center frequency of the resonant circuit and falls steeply off towards the channel limits.
A remote control receiver has also been proposed in which the number of cycles of the operating frequency arriving during a defined measuring period are counted and a control signal emitted as a function of the result of the count. For the precise analysis of the frequency received, the duration of the measuring period must be fixed precisely and kept very constant. The circuit stage determining the duration of the measuring period must be accurately adjusted before the start-up of the remote control receiver so that the desired counting results will accurately be obtained when counting the operating frequency cycles received.
Accordingly, it is an objective of the invention to provide a remote control receiver of the kind initially described which need not be tuned, incorporates a high protection factor against response to spurious received signals and can be entirely produced by integrated circuit technology.
A remote control receiver according to the invention includes an operating frequency counter which counts in repeated counting cycles respective operating frequency oscillations and emits an output signal when the counter reaches a predetermined count; a reference frequency counter which is controlled by the output signal of the operating frequency counter and counts the reference oscillations in each counting cycle of the operating frequency counter; a storage device to store a reference frequency counter count reached in a counting cycle; a comparator circuit which compares after each counting cycle the reference frequency counter count with the content of the storage device and produces, as the result of the comparison, a signal indicating agreement or nonagreement; and an error register arrangement which accepts and stores every comparison result and passes a control signal to the output associated with the particular operating frequency received only when a predetermined number of agreements has been reached.
In a receiver designed in accordance with the invention, an operating frequency counter counts a predetermined number of operating frequency oscillations. An output signal from the operating frequency controls a reference frequency counter so that the latter counts reference frequency oscillations for the period of time during which the predetermined number of operating frequency oscillations is received. The reference frequency counter count reached after the reception of the predetermined number of operting frequency oscillations, therefore, is directly related to the operating frequency received. The counter count reached in one counting cycle of the operating frequency counter can be stored in a storage device whose content is then compared in a comparator circuit with the new reference frequency counter count reached after each counting cycle of the operating frequency counter. The output signal of the comparator circuit indicating agreement or nonagreement of the compared values is supplied to an error register arrangement which produces a control signal at the output associated with the operating frequency received only after a predetermined number of successive, uninterrupted agreements of the compared values has been reached.
A remote control receiver embodying the invention can be constructed exclusively of circuit elements which do not have to be tuned to specific frequencies. Inasmuch as no coils are used, such a receiver is amenable to production completely in the form of an integrated circuit. Consequently the entire receiver may be produced in a form occupying but very little space.
A remote control receiver embodying the invention also provides a high degree of safety against temporarily occurring interference frequencies. Due to the fact that the error register arrangement enables the generation of the control signal at the output associated with the operating frequency received only after a predetermined number of agreements has been reached, an interference frequency of short duration stemming from an interfering transmitter will not activate the control signal because this control signal emission occurs only after a longer duration of that frequency received constantly and unchanged.
A remote control receiver embodying the invention is preferably designed so that the error register arrangement includes an output at which a signal is produced after a predetermined number of nonagreements has been reached; that the storage device presents an input connected to the output of the error register arrangement; and that the transfer of the reference frequency counter count into the memory is enabled as a function of the signal at the output of the error register arrangement. Due to this further development, the storage device does not accept every reference counter count, and this acceptance operation is triggered only if a signal is applied to a control input of the storage device.